This invention relates to novel compositions of matter. More particularly, it relates to cationic epoxy compounds that are water-soluble or water-dispersible and that contain both epoxy and organoonium functionalities. These compounds have utility in heat-sensitive compositions and imaging members such as lithographic printing plates.
Epoxy resins represent a very broad class of organic materials that have been found useful in a variety of applications both as bulk materials in and of themselves, as components in composite materials, and as crosslinkers for various polymers. A complete discussion of this multi-billion dollar industry and the huge variety of the chemistry and products involving epoxy resins is provided in a very large amount of literature. See, for example, Flick, Ernest W. Epoxy Resins, Curing Agents, Compounds, and Modifiers. An Industrial Guide, Noyes Data Corp.: Park Ridge, N.J., 1987 and Bruins, Paul F. Epoxy Resins Technology, Interscience: New York, 1968.
Despite the large amount of available epoxy technology, the overwhelming majority of the uses of epoxy resins involve the preparation of an end product (a bulk material or a coating) that is mechanically tough, resistant to the elements, chemical resistant, and very hydrophobic. Thus, known epoxy resins have not found extensive use in hydrophilic environments in which a net hydrophilic, water-swellable, water-compatible, or readily wettable end product is required. Such uses include bio-compatible materials, aqueous separations media, coatings for lithographic printing plates, and photographic materials.
The current global trend of reducing the amounts of volatile organic compounds permitted in industrial emissions has fueled a continuing interest in the development of useful technology for aqueous-based formulations and coatings for many uses including lithography or computer-to-plate imaging members. Consequently, advances in epoxy resin chemistry have allowed for the use of epoxy resins material in aqueous formulations. The most common strategy for the use of such epoxy resins in aqueous formulations has involved the preparation of aqueous dispersions of hydrophobic, water-insoluble epoxy resins. These dispersions are typically stabilized either by a surfactant or a protective colloid such as poly(vinyl alcohol). Many of these dispersions are sold commercially and a representative example of this type of system is described in U.S. Pat. No. 5,602,193 (Stark). This class of epoxy resins, though formulated in water, are still largely hydrophobic in nature and are not suitable for the applications noted above wherein the target material or coating must be highly wettable or must have a very high water uptake or water compatibility. These resins are also largely incompatible with many water-soluble polymers and multi-phase formulations may result when they are used.
There are a large number of patents describing cationic epoxy resins of the type that are commonly used in electrophoretic coating processes (also knows as electrodeposition coating). Most of these resins, however, contain a mixture of primary, secondary, and tertiary amine groups and are designed such that they can be rendered water-soluble by neutralization with an acid. This property is crucial to their described use, as the production of hydroxide by water reduction at the cathode deprotonates the resin, and the resin is then deposited on a metal surface. This process results in the deposition of a tough, water-insoluble coating on a metal surface in which all of the net charge of the epoxy resin has been destroyed (or neutralized). Examples of cationic amine salt-containing epoxy resins of this type are described for example in U.S. Pat. No. 4,487,674 (Jan Al et al.), U.S. Pat. No. 5,483,012 (Midogohchi et al.), and U.S. Pat. No. 4,208,262 (Kubo et al.).
Epoxy resins used for electrodeposition coating are also broadly described in ACS Symposium Series # 114 (Epoxy Resin Chemistry), pp. 57-69, (Vol. Date 1978), Journal of Coatings Technology Vol. 54, No. 688, pp. 35-44 (1982), and Journal of Coatings Technology Vol. 54, No. 686, pp. 33-41 (1982).
The solubility of the known epoxy resins used for electrodeposition resins is responsive to pH. There is a desired to have cationic epoxy resins where the solubility is not responsive to pH so there is more latitude in formulation.
U.S. Pat. No. 4,035,275 (Sturni et al.), U.S. Pat. No. 3,839,252 (Bosso et al.), U.S. Pat. No. 3,619,398 (Bosso et al.), U.S. Pat. No. 4,001,156 (Bosso et al.), U.S. Pat. No. 4,110,287 (Bosso et al.), U.S. Pat. No. 4,144,159 (Bosso et al.), U.S. Pat. No. 4,038,166 (Bosso et al.), U.S. Pat. No. 4,081,341 (Christenson et al.), U.S. Pat. No. 3,894,922 (Bosso et al.), U.S. Pat. No. 3,936,405 (Sturni et al.), U.S. Pat. No. 3,962,165 (Bosso et al.), U.S. Pat. No. 3,937,679 (Bosso et al.), U.S. Pat. No. 3,959,106 (Bosso et al.), U.S. Pat. No. 3,928,156 (Wismer et al.), and U.S. Pat. No. 4,001,101 (Bosso et al.) broadly describe epoxy resins that contain both epoxy units and various cationic moieties. The resins preferably are phenolic-based and thus are highly aromatic in nature. This would increase their hydrophobic nature also. These resins, thus, tend to be more hydrophobic in character than is desired for a number of aqueous formulations.
Thus, there is a need for cationic epoxy compounds that are not pH sensitive, can be readily formulated and used in hydrophilic (or aqueous environments), and do not lose their ionic charge in coated form.
This invention provides a water-soluble or water-dispersible, branched or unbranched compound comprising a backbone having covalently attached two or more epoxy moieties and one or more of the same or different organoonium moieties.
In preferred embodiments, the organoonium moieties are the same or different organoammonium moieties, the same or different organophosphonium moieties, the same or different organosulfonium moieties, or the same or different N-alkylated, positively charged nitrogen-containing heterocyclic moieties, all of which are described in more detail below.
The cationic epoxy compounds of this invention comprise both epoxy units and organoonium moieties that are covalently bound to a backbone. Furthermore, the resins are derived from epoxy-containing backbone precursors that contain at least 25% by weight of oxygen with the remainder being aliphatic hydrocarbons and halogens. These precursor compounds are soluble in water or water-miscible solvents. These cationic epoxy compounds prepared therefrom are useful in the formulation of hydrophilic, water-compatible, water-swellable, or water-wettable coatings and materials and have unexpectedly good solution compatibility with oppositely charged polyelectrolytes. In contrast to the epoxy compounds known in the art, the cationic epoxy compounds of this invention have non-aromatic, oxygen-rich backbones.
As most of the compounds of this invention are polydisperse materials having structures that will vary in degree of branching and the degree of functionalization (pendant moieties), it is implied that all descriptions of chemical compounds will apply to the mean, or average structure of each material. Thus, the compounds of this invention can be linear, partially branched to any degree, or fully branched in structure.
The compounds can be obtained from epoxy-containing xe2x80x9cprecursor compoundsxe2x80x9d that are branched or unbranched, monomeric, oligomeric, or polymeric compounds comprising at least 25% by weight of oxygen with the remainder of the weight comprising of aliphatic hydrocarbon and residual aliphatic haloalkyl groups (usually chloroalkyl groups). The oxygen atoms are covalently bound within the precursor compound as hydroxy, aliphatic ether, epoxy, or aliphatic ester moieties. Preferably, all non-epoxy moieties are either hydroxy or aliphatic ether groups. Preferably, the percentage of oxygen (by weight) in the precursor compounds is from about 30% to about 50%. It would be apparent to one skilled in the art that the backbones of the epoxy compounds of this invention and the precursor compounds have essentially the same percentage of oxygen. For purposes of this invention, xe2x80x9cbackbonexe2x80x9d refers to the compounds that result if the organoonium compounds are severed from the remainder of the compounds at the carbon-heteroatom bond connecting the organoonium compound and a hydrogen atom is added to provide stoichiometry.
There are no aromatic groups in the backbone of the compounds of this invention (either aromatic carbocyclic or heterocyclic groups). Thus, the compound backbones lack aromaticity.
Furthermore, the precursor compounds are soluble in water or water-miscible solvents such as various alcohols (such as methanol, ethanol, and propanol), tetrahydrofuran, acetonitrile, acetone, glycols (such as ethylene glycol and diethylene glycol), and methyl ethyl ketone.
Preferred precursor compounds are glycidylated carbohydrates and glycidylated polyglycerols. More particularly, representative branched or unbranched precursor compounds used to prepare the compounds of this invention are identified below as Precursors I, II, III, and IV, and Precursors I and II are most preferred: 
In these compounds, the R groups can be the same or different in each molecule and can be either hydrogen or a glycidyl moiety 
as long as at least two R groups are glycidyl moieties.
Furthermore, Precursors I-IV are also intended to represent branched variations of the simplified linear structures that are illustrated as well as oligomeric species that are formed by intermolecular coupling reactions. It should also be noted that certain methods of preparation of the compounds of this invention result in the presence of haloalkyl residues (in particular, Rxe2x80x94CH2Cl groups) as common byproducts. Though these units are not shown in the simplified structures in FIG. I, their presence in the structures described herein is implied throughout this document and in the descriptions herein.
In Precursor II, n is generally from 1 to 10, and preferably from 2 to 6.
Most preferred precursor compounds include but are not limited to the following materials: glycidyl ethers of sorbitol (Precursor I, sold by Esplit Chemicals under the tradename of CR-5L and by Nagase Chemicals under the tradename of EX-611), of other reduced or non-reduced sugars polysaccharides, or of cellulosics, polyglycerol glycidyl ethers (Precursor II, sold by Nagase Chemicals under the trademark of Denacol(copyright) EX-521 and EX-512), pentaerythritol polyglycidyl ethers (Precursor III, sold by Nagase Chemicals under the trademark of Denacol(copyright) EX-313 and EX-314), trimethylolpropane polyglycidyl ethers (Precursor IV), glycerol polyglycidyl ethers, poly(ethylene glycol) diglycidyl ethers, glycidyl ethers of poly(vinyl alcohol), and poly(propylene glycol) diglycidyl ether.
The compounds of this invention generally have an average molecular weight of from about 250 to about 1,000,000 daltons. Preferably, the average molecular weight will be from about 250 to about 200,000 daltons, and more preferably, from about 274 to about 20,000 daltons.
It should be noted that, when a nucleophile is reacted with a glycidyl unit on one of the precursor compounds, substitution occurs most commonly at the least hindered (terminal) oxirane methylene carbon. However, multiple substitutions at other positions can also occur. The precursor compounds described herein are intended to include epoxy resins in which nucleophilic substitution has occurred at either position of the oxirane ring.
The compounds of this invention will contain, on average, two or more epoxy moieties and one or more of the noted organoonium moieties described below. It will be noted that where the compounds include two or more organoonium moieties in the same molecule, those organoonium moieties can be the same or different. In addition, the compound may contain pendant hydroxyl groups.
As noted above, the compounds of this invention are water-soluble or water-dispersible. The water-soluble compounds are most preferred. By xe2x80x9cwater-solublexe2x80x9d is meant that at 60xc2x0 C., a 2% (by weight) solution of the compound yields a clear solution in water from which no more than 5% of the compound can be recovered by filtration. By xe2x80x9cwater-dispersiblexe2x80x9d is meant that at least 2% (by weight) of the compound can be dispersed in water at room temperature without the use of an emulsifying agent to provide a two-phase system that exhibits no observable settling of the solid phase or phase separation after one hour.
The compounds of the present invention may be prepared or used as heterogeneous mixtures, and such mixtures may have both water-soluble and water-dispersible fractions.
Useful organoonium moieties include organophosphonium moieties, organosulfonium moieties, and organoammonium moieties as illustrated in the following Structures V, VI, and VII, respectively: 
R1, R2, and R3 are independently substituted or unsubstituted alkyl groups having 1 to 12 carbon atoms (such as methyl, ethyl, n-propyl, iso-propyl, hexyl, hydroxymethyl, cyanomethyl, methylenecarboxyalkyl, and dodecyl groups), substituted or unsubstituted carbocyclic or heterocyclic aryl groups having 5 to 10 carbon and/or heteroatoms in the ring (such as phenyl, naphthyl, pyridinyl, tetrahydropyranyl, tetrahydrofuranyl, and p-methylphenyl), and substituted or unsubstituted cycloalkyl groups having from 5 to 10 carbon atoms in the carbocyclic ring (such as 1,3- and 1,4-cyclohexyl groups). Alternatively, any two of R1, R2, and R3 can be combined to form a substituted or unsubstituted heterocyclic ring with the charged phosphorus, sulfur or nitrogen atom, the ring having 4 to 8 atoms in the ring. Such heterocyclic rings include, but are not limited to, substituted or unsubstituted morpholinium, piperidinium, pyrrolidinium, quinuclidine, tetrahydrothiophene, tetrahydrothiopyran, phospholane, and phosphinane groups. The various groups can also include one or more oxy, thio, carbonyl, amido, or alkoxycarbonyl groups.
Preferred R1, R2, and R3 groups are substituted and unsubstituted alkyl groups having 1 to 3 carbon atoms, and methyl and ethyl groups are more preferred. When two or more of R1, R2, and R3 are combined, preferably, they are combined to form 5- or 6-membered rings.
In addition, R1, R2, and R3 can contain additional organoonium groups as substituents. For example, R1, R2, or R3 can be a trimethylammoniomethyl group or a dimethylsulfoniomethyl group, thereby giving a pendant group with a net charge of +2.
Additional organoonium moieties useful in the practice of this invention are N-alkylated positively charged nitrogen-containing heterocyclic moieties that can be represented by the following Structure VIII: 
In Structure VIII, R4 is a branched or unbranched, substituted or unsubstituted alkyl group having from 1 to 12 carbon atoms (such as methyl, ethyl, n-propyl, iso-propyl, t-butyl, hexyl, methoxymethyl, benzyl, neopentyl, and dodecyl) or carbocyclic or heterocyclic aryl groups (as defined above). Preferably, R4 is a substituted or unsubstituted, branched or unbranched alkyl group having from 1 to 6 carbon atoms, and most preferably, it is substituted or unsubstituted methyl group.
R5 can be a substituted or unsubstituted alkyl group (as defined above, and additionally a cyanoalkyl group, a hydroxyalkyl group or alkoxyalkyl group), substituted or unsubstituted alkoxy having 1 to 6 carbon atoms (such as methoxy, ethoxy, isopropoxy, oxymethylmethoxy, n-propoxy, and butoxy), halo (such as chloro and bromo), a substituted or unsubstituted carbocyclic or heterocyclic aryl group (as defined above), a substituted or unsubstituted cycloalkyl group having 5 to 8 carbon atoms in the ring (such as cyclopentyl, 1,3-, or 1,4-cyclohexyl, and 4-methylcyclohexyl), or a substituted or unsubstituted non-aromatic heterocyclic group having 5 to 8 atoms in the ring including at least one nitrogen, sulfur, or oxygen atom in the ring (such as pyridyl, pyridinyl, tetrahydrofuranyl, and tetrahydropyranyl). Preferably, R5, is substituted or unsubstituted methyl or ethyl group.
Zxe2x80x3 represents the carbon and any additional nitrogen, oxygen, or sulfur atoms necessary to complete the 5- to 10-membered aromatic N-heterocyclic ring that is attached to the polymeric backbone. Thus, the ring can include two or more nitrogen atoms in the ring (for example, N-alkylated diazinium or imidazolium groups), or N-alkylated nitrogen-containing fused ring systems including, but not limited to, substituted or unsubstituted pyridinium, quinolinium, isoquinolinium acridinium, phenanthradinium, and other groups readily apparent to one skilled in the art. Preferred groups of this type are pyridinium groups.
Also in Structure VIII, m is 0 to 6, and it is preferably 0 or 1. Most preferably, m is 0.
The most preferred compounds of this invention include organoonium moieties as represented by the following Structures C, D, E, F, and G in which the organoonium moieties are attached to the compound backbone. 
In Structures C-G, Rxe2x80x2, R1, R2, and R3 are as defined above, xe2x80x9cHetxe2x80x9d represents an N-alkylated heterocyclic group illustrated in Structure VIII above, and X+ can be any of the organoonium groups described herein.
Rxe2x80x2 is a divalent unreactive organic linking group capable of connecting the ester unit to the organoonium moiety. Preferably, Rxe2x80x2 is a substituted or unsubstituted alkylene or cycloalkylene group, and most preferably, it is a substituted or unsubstituted alkylene having 1 to 3 carbon atoms.
While the compounds of this invention will contain one or more or the same or different organoonium moieties and two or more epoxy moieties, preferably, the molar ratio of epoxy moieties to organoonium moieties is from about 19:1 to about 1:19. More preferably, this molar ratio will range from about 4:1 to about 1:4.
The cationic epoxy compounds of this invention are synthesized by chemical modification of the epoxy-containing precursor compounds. Generally, one or more neutral, nucleophilic heteroatom compounds (such as trialkyl amines, dialkyl sulfides, trialkyl phosphines, or nucleophilic, nitrogen-containing heterocycles) and a protic acid (one equivalent of protic acid per equivalent of nucleophilic compound) will be combined with the precursor compound in water, a water-miscible organic solvent, or a mixture thereof. The protic acid can be any organic or mineral acid with a sufficiently non-nucleophilic, non-reactive conjugate base. Hydrochloric acid is a preferred protic acid.
The amount of the neutral, nucleophilic heteroatom compound will be such that complete conversion will afford a compound that will contain more than one epoxy moiety and at least one cationic organoonium moiety per average molecule. Reaction temperatures will generally range from room temperature to 100xc2x0 C. More commonly, the reaction temperature will be from about 40 to about 60xc2x0 C. The reactions will typically be run at 5-90% solids. It has been found, however, that at reactions carried out at 10-20% solids and temperatures of less than 60xc2x0 C. provide optimal conversions (yield) with minimal growth of molecular weight and very little, if any, gelation. The reaction can be conveniently monitored by observing the disappearance of the oxirane protons using proton NMR or by monitoring the disappearance of the nucleophilic heteroatom compound by gas chromatography or ion chromatography. The desired compound can be stored and used in solution in the reaction solvent. Alternately, the solvents can be stripped under vacuum to afford the desired compound resin or the desired compound can be isolated by precipitation into an appropriate non-solvent.
In another embodiment of this invention, the epoxy-containing precursor compound can be reacted via the method described above with a reactant compound containing an organoonium group linked to a carboxylic acid. In this case, a protic acid is not needed. An example of such a reactant compound is betaine hydrochloride. Such a reaction will afford a cationic compound in which the organoonium group is linked to the backbone by an ester linkage to afford a compound that contains pendant moieties identified as Structure E.
It is also possible to prepare and use a mixture of two or more water-soluble or water-dispersible, branched or unbranched compounds of this invention. The compounds would comprise the same or different backbones, each backbone having covalently attached thereto, two or more epoxy moieties and one or more of the same or different organoonium moieties. This mixture of compounds can be prepared by reacting a mixture of precursor compounds noted above with the appropriate amounts and types of reactants, depending upon the reaction scheme that is used. The mixture of compounds can be isolated or used in solution.